There is a retinal receptor called “melanopsin” that detects light and uses it to help regulate melatonin production, which is involved in initiating the sleep cycle in a human. Visible light, including wavelengths from approximately 390 nm to approximately 700 nm on the electromagnetic radiation spectrum, is known to have measurable effects on the melanopsin receptors. Additionally, the duration of light exposure, the intensity of light, and the time of day during which the exposure occurs contribute to the regulation of the circadian rhythm in humans. As a result, the human circadian rhythm may be advanced or delayed by manipulation of light exposure.
The body's natural circadian rhythms, which are mediated by local day/night cycles and exposure to light, become disrupted when the day/night cycle at a new location, subsequently referred to as “Destination,” does not match the day/night cycle from a previous location to which the body is still acclimated, subsequently referred to as “Origin.” This effect is called circadian desynchrony, including the effect known colloquially for air travel, as “jet lag,” and occurs when a person, such as a passenger or crew member, travels across a number of times zones in a period of time that is shorter than the body's ability to acclimate to the Destination time zone. The natural adjustment to a Destination time zone takes approximately one day for every time zone crossed, but can take longer or shorter depending on the individual. On average, if a person has rapidly travelled across three time zones to a Destination, it will take approximately 3 days before that person's circadian rhythm readjusts to the new day/night light cycle. Resulting effects of such disruption include excessive sleepiness or inability to sleep, decreased appetite, and general malaise. The circadian desynchrony exists as soon as the user is out of his/her acclimated day/night cycle time zone.
For example, if a passenger flies from an Origin city in the US Central Time Zone at 7:00 AM to London, England, the arrival time of 9:00 PM time at the Destination (London) is the equivalent of 3:00 PM Central at the Origin. The passenger's body will be expecting up to 6 additional hours of daylight that is not available at the Destination, and this sudden loss of daylight may have an effect on the circadian rhythm of the passenger.
Existing solutions include trying to speed up the adjustment to a new time zone by forcing the body into a new sleep/wake schedule in advance of the trip or taking supplemental doses of melatonin or other sleep aids or stimulants. Melatonin supplements and other sleep aids or stimulants can have negative side effects and limited usefulness. New sleep/wake schedules are not every effective since they conflict with the pattern of light exposure in the Origin, to which the body is still acclimated.
A passenger on any vehicle, such as an aircraft, that will result in a time zone change from Origin to Destination may experience jet lag. For time zone changes of less than three hours, there are typically minimal effects that are resolved in one to two days and do not significantly disrupt sleeping and eating schedules and contribute to significant feelings of discomfort or malaise. For time zone changes of three or more hours, the negative effects of jet lag are more pronounced and the effects of light-induced mitigation are greater. A system and method are proposed to mitigate the impact of jet lag associated with disruptions in circadian rhythms that users such as passengers, experience after long flights, particularly those that cross time zones that result in a rapid shift in time greater than or equal to three hours.